# Motors spin slowly while disarmed **URL:** \ **Category:** Modifications\ **Created:** [April 13, 2021, 12:01am UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451 "2021-04-13T00:01:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Paul\_461](https://avatars.discourse-cdn.com/v4/letter/p/3ab097/32.png) [@Paul\_461](https://discuss.bluerobotics.com/u/Paul_461)\ **Post date:** [April 13, 2021, 12:01am UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/1 "2021-04-13T00:01:24Z")
We are building a mock-up for experimentation with our school group. I have an Unbuntu 20.04 top side computer with Qgroundcontrol 4.0.5, the companion Raspberry Pi 0.0.26 and a Pixhawk with Ardusub 4.0.3. The frame type is a simplerov 4. I purchase four inexpensive bi-directional ESCs which claimed they did not require calibration and brushless motors . As soon as the power is applied the motors begin to spin slowly. I checked them with a PWM tester and discovered they will spin at 1500us and become neutral between 1478 and 1496us. The MOT\_PWM\_TYPE is normal. I have tried changing the parameters SERVOn\_TRIM and RCn\_TRIM to 1486us, I changed the RCn\_DZ to numbers between 20 and 40, and have changed the MOT\_SAFE\_DISARM from PWM enabled while disarmed to PWM disabled while disarmed. Without any change. When it is armed all of the motors spin normally. Is there anything else I should or could try? ---
**Author:** ![subsearovers](https://avatars.discourse-cdn.com/v4/letter/s/a6a055/32.png) [@subsearovers](https://discuss.bluerobotics.com/u/subsearovers)\ **Post date:** [April 17, 2021, 7:15pm UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/2 "2021-04-17T19:15:09Z")
Our robotics team had the same issue using six T-100s and Basic ESCs. We monitored the outputs to the ESCs from the uC with a scope and didn’t see any good reason for the movement. Sometimes the motors would go forward and sometimes reverse IIRC. We tried 4 different uCs over the course of 4 years and that had no effect on the motion. When we went from 4 thrusters to six, we switched to the newer ESCs and still had the issue. ---
**Author:** ![williangalvani](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@williangalvani](https://discuss.bluerobotics.com/u/williangalvani)\ **Post date:** [April 19, 2021, 11:57am UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/3 "2021-04-19T11:57:39Z")
Hi @Paul_461 , Unfortunately, the center pwm for the ESCs is fixed at 1500us right now. If you don’t mind setting up the tooling to build ardupilot, (which can take some work), you could change 1500 to your center in file [AP\_Motors6DOF.cpp](https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Motors/AP_Motors6DOF.cpp#L235) (lines 228 and 235). ---
**Author:** ![TKopi](https://avatars.discourse-cdn.com/v4/letter/t/da6949/32.png) [@TKopi](https://discuss.bluerobotics.com/u/TKopi)\ **Post date:** [May 3, 2021, 9:10pm UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/4 "2021-05-03T21:10:28Z")
Hi guys, I have similar problem with slowly spinning motors after disarming. I tried to configurate a dead zone and trim, but RC settings in Q GroudControl are not synchronizing with Pixhawk unit (there is no changes after changing the trim value to 1480, for example). I’m using an [official ArduPilot firmware for Pixhawk ([ArduPilot firmware : /Sub/latest/Pixhawk1](https://firmware.ardupilot.org/Sub/latest/Pixhawk1/)) but not sure where I can find a mentioned file (AP\_Motors6DOF.cpp file) in firmware structure. @williangalvani can you please navigate me? Thanks! ---
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [May 4, 2021, 10:52am UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/5 "2021-05-04T10:52:55Z")
> [@TKopi](#): > > I’m using an [official ArduPilot firmware for Pixhawk The location you’ve linked to here is for pre-built binaries of ArduSub. @williangalvani is talking about a file that is used when creating those binaries, and links directly to where that file is located in the source code repository in his comment. If you make changes in that file then to apply them to your pixhawk you’ll need to build a new version of ArduSub using your modified file, and upload the generated file. ---
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [September 30, 2025, 3:07pm UTC](https://discuss.bluerobotics.com/t/motors-spin-slowly-while-disarmed/9451/7 "2025-09-30T15:07:11Z")
I just came across this while looking for something else, and thought I’d follow up that this is a solved problem now. Motor trim is available in ArduSub \>= 4.5.3, by > [@How to change neutral set point for motors](https://discuss.bluerobotics.com/t/how-to-change-neutral-set-point-for-motors/20987/3): > > … setting the [`SERVOn_TRIM`](https://ardupilot.org/sub/docs/parameters.html#servo1-trim-trim-pwm) parameters for your motor pins …, with [`MOT_PWM_TYPE`](https://ardupilot.org/sub/docs/parameters-Sub-stable-V4.5.3.html#mot-pwm-type-output-pwm-type) set to `PWMAngle (9)`.